Running thicker Headgasket Question

[slowvac]

Hi,

Since my head had been taken off for some work. I would like to know what gasket should I use?
What are the pro and cons of running a thicker headgasket (apart from running more boost)?

I have bought ACL 1.6mm Copper and Cometic and OEM 1.3mm MLS

Cheers.

 

[4piknup]

hi and welcome
the old school thought was that copper gaskets needed fire rings machined into top of block. i presume this is still the case.
the mls should have a different machine finish to the block and head (finer finish i think?) for maximum reliability.

 

[benozi]

I would use the mls one. ive heard copper ones dont blow as easy and it dosnt act as a weak link

 

[JC evo1]

Without a doubt run the oem gasket. Its a bad idea to use a thicker gasket to change compression ratio, making the quench distance bigger can lead to problems.

 

[CYBORG-X]

pros- generally a tougher headgasket (copper) you dont need to 'o' ring it tho
thats about it...
cons- decompresses motor
reduces squish band
creates localised heat


copper, o ringing, and thick head gaskets are all dinosaur technologys... mls is by far the better choice

 

[bazeng]

Find out the cr your tuned wants and use the gasket to suit. Or decide what you want in cr and use the gasket to suit.

Basically higher cr = more off boost power and less boost potential. Lower cr = less off boost power but more boost potential. The rules change on high octane fuel though.

 

[DOUGMO]

as JC says, its not always better to run a thicker gasket to lower comp.

I now run a thinner than stock gasket but with a lower CR than I had when I ran the 1.3mm gasket.

And from my limited experience with copper gaskets I wouldt even consider them at all.

 

[slowvac]

Thanks for all the reply. At the moment the head has been cleaned up around the chamber with minor ported on exhaust and fully ported and polished intake (all done diy with a mate backyard shead) waiting to be flow balanced on a homemade flow benched . The reason for the madness is that since I have taken the head off the car I'm concentrating on getting the maximum potentital from the head using the stock bottom end and stock turbo with 10.5 housing.

Cheers.

 

[4piknup]

show us the homebrew flow bench and how it works

 

[slowvac]

Hi all again,

It had been a busy time. My friend did not have a chance to get the head flowed (But he was satisfied that the head will perform well). I took my head to a machinest and they told me that I could not use the factory MLS gasket as the combustion chamber was slightly to much (just past the sealing ring). The only way is to use a copper gasket and grind the combustion chamber to fit. Now the head has been bolted up on the car and in a couple of weeks the car will be back on the road.

Cheers.

 

[bazeng]

Please clarify:

Slightly too much? As in cr too high? Or Pistons wont clear the head at tdc?
Or bore too big?

I dont see the reason why you need a copper gasket. You can get mls gasket up to 1.9mm from the last time I was looking which is considered thick. Tomei were the ones doing it. If big bore is required, Cometic do them +80 thou last time I checked. If the Pistons protrude too much, get custom Pistons to suit your desired cr.

 

[slowvac]

Barry,

The bores size are still factory spec (haven't touched the bottom end). My friend got a bit to excited when cleaning the combustion chamber on the head with the grinder. What happen is when placing the OEM gasket over the head the gasket would not have sealed properly. The only solution is to either run a big bore gasket/custom MLS or copper(which is one peice and can be modified to fit and won't effect the gasket integerity (from what I was told)). Only time would tell.

Once I get my car back on the road. I'll pop over and show the pictures and show what I'm talking about.

Once this was all the inital head issues I had. I already ordered a performance head and cam combo from the US for a replacement but now is spare for the future project (very expensive coffee table/stool at the moment, but it would have been interesting to see how it performed with the stock bottom end).

Cheers.

 

[JC evo1]

maybe a fel pro mls will work, its bit over 87mm from memory

 

[JC evo1]

also, i would not recommend copper either

 

[slowvac]

At the moment I'm running copper gasket on the car. So far so good. I've done 400km and done the first round of re-torquing the head at 80lb. My mate told me that I have torque the head 3 more time to make sure nothing will happen.

So far the modified head made a big differences with the car.

Cheers.

 

[slowvac]

Update. The head was pulled down again as coolant was getting pushed out of the radiator. Found that the copper gasket did not seal causing cooling and oil pressure issues. So a factory modified gasket was used and got the car running with no issue (clocked 2000km since Christmas eve). We believed the copper gasket we used has not been annealed which would have moulded with sealing area.
The copper gasket would have been good but unfortunately it did not work in my situation..

Cheers

 

[Lister]

Generally speaking, I've always found people having issues sealing copper head gaskets. More often than not they cause headaches. Glad to hear a mls is working for you.